1. Field of the Invention
The present invention relates to a refrigeration system, which includes a refrigeration cycle and a Rankine cycle.
2. Description of Related Art
Japanese Unexamined Patent Publication No. 2006-46763 (corresponding to U.S. Publication No. 2006/0026981A1) discloses one refrigeration system. This refrigeration system includes a refrigeration cycle and a Rankine cycle, which recycles waste heat of an internal combustion engine (serving as a heat generating apparatus). The refrigeration cycle includes a compressor, which compresses and discharges refrigerant, and the Rankine cycle includes an expansion device, which is operated through expansion of the refrigerant that is heated by the waste heat. A condenser of the Rankine cycle is shared with the refrigeration cycle.
In such a refrigeration system, one of a sole operation of the refrigeration cycle, a sole operation of the Rankine cycle and a simultaneous operation of both of the refrigeration cycle and the Rankine cycle is performed depending on a need for cooling a passenger compartment of the vehicle and a recoverability of the waste heat.
In the above refrigeration system, during the sole operation of the Rankine cycle, the refrigerant or lubricant oil (for lubricating devices) contained in the refrigerant may possibly be accumulated in the refrigeration cycle. This may cause a reduction in a basic performance of the Rankine cycle or insufficient lubrication of the corresponding devices of the Rankine cycle, which require lubrication. Inventors of the present application have previously proposed a technique for addressing the above disadvantage. According to this technique, the compressor is turned on and turned off at predetermined timing to limit the accumulation of the refrigerant or the lubricant oil in the refrigeration cycle.
However, when the compressor is operated during the sole operation of the Rankine cycle, a flow quantity of the refrigerant, which is supplied to the condenser, is rapidly increased. This will deteriorate the performance of the condenser. Therefore, a sufficient amount of liquid refrigerant cannot be supplied to a heating device. As a result, a pressure difference between an upstream side and a downstream side of the expansion device is reduced, and thereby the rotational drive force cannot be obtained at the expansion device. Thus, the Rankine cycle cannot function properly.